sci-fi
Ender's Game - I've read or listened to this more times than I can remember. I've also read it to my daughters when they were in about 6th grade. Will read it to my son in a couple of years.

I've read and reread most of the other books in the Enderverse. Speaker for the Dead has the most rereadability

All of John Scalzi's books except God Engines (once was enough)

Though I haven't reread them yet, I plan to reread all of the Expanse novels as well as Game of Thrones.

fiction
Chaim Potok's The Chosen and also The Promise. These books helped me immensely as a teenager dealing with weighty family issues. I revisit them about every 5 years.

nonfiction
I've read a lot of Ambrose and tend to reread his WWII books every 5 to 10 years.